National Coral Reef Monitoring Program

Climate Monitoring Brief: Flower Garden Banks National Marine Sanctuary

Coral reef at East Buoy 3 in the Flower Garden Banks

Coral reef at East Buoy 3 in the Flower Garden Banks


Atlantic Oceanographic & Meteorological Laboratory Coral Program
University of Miami Cooperative Institute of Marine and Atmospheric Science
National Oceanic and Atmospheric Administration


N. Besemer, A. Palacio, B. Ross, I. Enochs - February 2026

Mission

The AOML Coral Program tracks the status and trends of coral reef ecosystems of the U.S. Atlantic and Caribbean as part of the National Coral Reef Monitoring Program (NCRMP). This summary brief provides an overview of the most recent climate monitoring efforts at Flower Garden Banks National Marine Sanctuary (FGBNMS).

Expedition summary

Data collection summary

Subsurface temperature

Subsurface temperature recorders (STRs) were recovered and redeployed at east and west bank transects, including four instruments per bank ranging in depth from 20m to 35m (Fig. 1). In total, more than 1.5 million temperature observations were collected (Table 1).

Table 1: Number of temperature observations collected by transect and depth
Transect 20m 25m 30m 35m Total
East 106,301 286,645 125,259 304,312 822,517
West 61,526 83,070 304,244 303,787 752,627
Figure 1: Study sites and depths in Flower Garden Banks

Figure 1: Study sites and depths in Flower Garden Banks

NCRMP Climate Fixed Sentinel Site Monitoring

At East Buoy 3, 20m site, located on the East Bank, short term instruments (72h) were deployed to monitor daily fluctuations in:


Habitat persistence

Changes in Bioerosion and accretion were monitored


Coral core collection

Every 5-10 years, the Coral Program field team collects coral cores as a part of NCRMP to track coral growth over time (Fig. 2). In this cruise, we collected 16 cores across three species: 11 Orbicella faveolata, 3 Colpophyllia natans, and 2 Pseudodiploria strigosa.

Figure 2: NCRMP diver collects a coral core at the FGB.

Figure 2: NCRMP diver collects a coral core at the FGB.

Subsurface Temperature

The temperatures that marine organisms experience are a function of depth and local oceanographic conditions. To monitor this, two cross-shelf transects were established at each bank within the sanctuary. Three years of temperature measurements were retrieved and processed from eight sites (depths). Each transect consists of STRs at 4 depths (20, 25, 30, 35m; Fig. 3). Temperature was measured using SeaBird Electronics Subsurface Temperature Recorders (STRs) that collected data at 5-minute intervals. Gaps exist in the data as some STRs battery life died before the end of the full deployment.

Figure 3: Temperature conditions at two transects in FGBNMS (east bank, and west bank) representing a depth gradient (20m, 25m, 30m and 35m). The dots in the left panels curves represent the last time point available for each transect and depth.

In general, the lowest temperatures were recorded during the winter of 2024 at both the east and west banks. In February 2024, minimum temperatures ranged from 19.2 to 19.4 \(^\circ\)C, while maximum temperatures fluctuated between 21.4 and 21.7 \(^\circ\)C. September 2023 was the warmest month at both banks, with mean temperatures exceeding 30.2 \(^\circ\)C at the East 20m, 25m, and 30m stations and at the West 30 m station. Mean temperatures at the 35m stations on both banks were slightly lower, averaging 29.8 and 30.0 \(^\circ\)C, respectively (Fig. 3).

Sentinel Site Monitoring (Diurnal Suite Deployment)

Seawater carbonate chemistry can fluctuate diurnally, due to biological forcing and processes such as photosynthesis and respiration, as well as calcification and dissolution. To characterize this, discrete water samples were collected at three-hour intervals (n=20) using Subsurface Automatic Samplers (SAS, https://www.coral.noaa.gov/accrete/sas/). These samples will be analyzed for Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), and Spectrophotometric pH (SpecpH), which will be used to calculate pCO2 and aragonite saturation state (ΩAragonite).

A suite of instruments was deployed for a 72-hour period at the East Bank 20m site. A SAMI was used to log pH, an EcoPAR measured Photosynthetically Active Radiation (PAR), and a Lowell Tiltmeter measured current speed and direction. Each instrument collected measurements at 15-minute intervals (Fig. 4).

Figure 4: Data from East Buoy 3 diurnal suite monitoring from August 26th to August 29th. Top panel: pH and temperature from SAMI pH. Bottom panel: Photosynthetically Available Radiation (PAR) and current speed from EcoPAR and Tiltmeter. Grey blocks denote night time throughout sequence of the plot. Instruments measured parameters every 15 minutes.

Habitat persistence

Carbonate budget assessments use transect-based surveys to quantify the abundance of carbonate producers, such as corals and crustose coralline algae, as well as carbonate bioeroders, such as grazing parrotfish and sea urchins (Fig. 5). Abundances are multiplied by taxon- specific rates of carboante alteration to determine if a reef is in a state of net accretion (habitat growth) or net loss (habitat loss). At East Buoy 3, six transects were established and surveyed in 2015 to obtain carbonate budgets. We revisited this site in 2019, 2022 and 2025 to assess the evolution of carbonate budget after ten years.

Figure 5: NCRMP Diver conducting a carbonate budget survey.

Figure 5: NCRMP Diver conducting a carbonate budget survey.

Carbonate budgets have remained positive during the monitoring period (2015-2025), indicating continued habitat growth. However, they declined in 2022 and 2025. In 2022, intense bioerosion by parrotfish, driven by the presence of very large individuals across the transects, led to a fourfold increase in parrotfish bioerosion rates between 2019 and 2022. Combined with reduced coral cover, this resulted in a decline in net community calcification exceeding 4 kg m⁻² yr⁻¹ in 2022. In 2025, parrotfish bioerosion was less pronounced; however, coral production remained low. Consequently, carbonate budgets were higher than in 2022 but still lower than those recorded in 2015 and 2019 (Fig. 6).

Figure 6: Carbonate budgets from East FGB in 2015, 2019, 2022 and 2025 (left panel) and the processes contributing to calcification and bioerosion (center and right panels). The horizontal line in the “Net carbonate production panel” denotes accretionary stasis, the point where the budget flips from habitat growth to loss. PF represents parrotfish.

Landscape mosaics are used to quantify the benthic community, and to monitor changes in coral cover over time (Fig. 7). Thousands of underwater images are digitally stitched together to create a high-resolution archive of the reef at the time of collection.

Figure 7: Landscape Mosaic collected from transect 6

Figure 7: Landscape Mosaic collected from transect 6

Finally, Calcification Accretion Units (CAUs) and Bioerosion Monitoring Units (BMUs) were used to investigate the balance between calcification and erosion. CAUs and BMUs were collected and redeployed for the next sampling cycle. CAUs are processed by the Pacific Climate group and the data will be available within a year. BMUs will be dried and cleaned using a hydrogen peroxide solution. These samples will be weighed and scanned using a CT scanner and then compared to their pre-scans to quantify bioerosion. Data will be available in a year. Please reference previous datasets for more information.

About the monitoring program

AOML’s climate monitoring is a key part of the National Coral Reef Monitoring Program of NOAA’s Coral Reef Conservation Program (CRCP), providing integrated, consistent, and comparable data across U.S. managed coral reef ecosystems. NCRMP efforts aim to:

Point of Contact

Atlantic Climate Operations Coordinator:

Principal Investigator:

NCRMP Coordinator:

For more information

Coral Reef Conservation Program: http://coralreef.noaa.gov

NCRMP environmental monitoring: https://www.coris.noaa.gov/monitoring/climate.html

NOAA Atlantic Oceanographic and Meteorological Laboratory: http://www.aoml.noaa.gov/

FGBNMS Reef Status Report 2020

National Coral Reef Status Report 2020

Acknowledgements

These efforts were jointly funded by NOAA’s CRCP project #743 and OAP. We would like to sincerely thank Flower Garden Banks and the National Marine Sanctuary Foundation for supporting our field efforts and assisting monitoring surveys and permitting.

Our Team

Flower Garden Banks 2025 Field team

Flower Garden Banks 2025 Field team

AOMLs NCRMP Atlantic and Caribbean Climate Team: I. Enochs, N. Besemer, A.Boyd, M. Jankulak, A. Palacio-Castro, A. Webb, B. Chomitz

Field team support and collaborators: R. Karp, P. Kiel, A. Rossin, T. Gill, J. Morris, E. Delilo, K. O’Connell, M. Studivan